The present invention relates to a method and apparatus for electronic temperature sensing. More specifically, the present invention is directed to improving setup times for sampling a voltage from a temperature sensor by using a constant offset buffer to isolate an analog-to-digital converter from the temperature sensor.
Temperature sensors are often employed to measure temperatures in a remote system. One type of temperature sensor includes a semiconductor device such as a PN junction. A PN junction conducts a current when forward biased. The PN junction has an associated voltage drop that is determined by the forward bias current and the temperature of the PN junction. Voltage drops across the PN junction are measured for two different forward bias currents. An analog-to-digital converter (ADC) may be employed to convert the voltage drops across the PN junction to digital data. The digital data is recorded and analyzed to determine the temperature of the PN junction.
The present invention is directed to a data acquisition system for sampling a temperature signal from a temperature sensor that includes a semiconductor sensor. More specifically the present invention is directed towards a method and apparatus that improves setup times for sampling the temperature signal by using a constant offset buffer to isolate the sampling transients of an analog-to-digital converter from the temperature sensor.
A data acquisition system for sampling a temperature signal from a temperature sensor includes: a programmable current source, a buffer with a constant offset, and an analog-to-digital converter (ADC). The programmable current source selectively provides bias currents to the temperature sensor, which produces response voltages in response to the applied bias current. The buffer receives the response voltages and produces buffered response voltages that include a constant offset. The constant offset allows the constant offset to be subtracted from successive measurements from a temperature sensor. The ADC is arranged to produce values in response to the buffered response voltages. The values are used to determine a temperature associated with the temperature sensor. The buffer isolates the temperature sensor from the ADC such that loading effects are minimized and set-up times for the conversion are minimized.